jQuery.getScript加载同域JS的代码

varloadScript=function(url,callback,charset){
varhead=document.getElementsByTagName("head")[0];
varscript=document.createElement("script");
if(charset){
script.charset=charset;
}
script.src=url;
if(!callback){
return;
}
script.onload=script.onreadystatechange=function(){
if(!this.readyState||this.readyState==="loaded"||this.readyState==="complete"){
callback();
}
};
head.appendChild(script);
};